1. Field of the Invention
The present invention relates to a motor driven bell sound generating system in which a small motor is incorporated for energizing the system, and more particularly to a bell sound generating system constructed such that rotational movement of the motor is converted into reciprocative or turning operation of the hammer, hammer arm or hammering rod so that striking or hammering effect is imparted to the bell gong which serves as a sound source.
2. Description of the Prior Art
Electrically driven bells are widely known in the art including those having electromagnetically driven hammer means for generating a bell sound. To facilitate the understanding of the invention this kind of the conventional electromagnetically driven bell sound generating system will be briefly described with reference to FIG. 1 as follows.
As illustrated in FIG. 1, a bobbin 2 with a magnetic core 2a inserted therein and a stationary contact plate 3 are securely mounted on the yoke 1, while a vibratory plate 5 having a leaf spring 4 connected thereto at its bottom portion is rotatably supported by means of the vertically extending support members on the yoke. On the extreme end of said leaf spring 4 is formed a contact 4a, while on the top end of said stationary contact plate 3 is formed another contact 3a. Further a lead wire 6 is extended from the one end of the coil 2b on said bobbin 2, while another lead wire 7 is extended from the bottom portion of said stationary contact plate 3. Further on the top end of said vibratory plate 5 is arranged a hammer 8 secured thereto at the bottom portion thereof, said hammer 8 being extended through an opening on the yoke 1. A coil spring 9 is arranged about the hammer 8, one end of said coil spring 9 being connected to the yoke 1 in the vicinity of said opening. The bell gong 10 is located at the predetermined distance from the extreme end of the hammer 8.
As direct current is applied to the lead wires 6 and 7, it flows through the lead wire 6, the coil 2b, the contact 4 on the leaf spring 4 and the contact 3a on the stationary contact plate 3 to the lead wire 7. As the bobbin 2 is energized, attractive force is produced through the magnetic core 2a, whereby the vibratory plate 5 is drawn toward said magnetic core 2a. Thus the hammer 8 is displaced against the coil spring 9 so as to strike the inner wall of the bell gong 10. At the same time the contact 3a is parted away from the other contact 4a, causing the electrical current flow to turn off. The magnetic core 2b becomes demagnetized and thereby the vibratory plate 5 is restored to the original position by means of the resilient force of the coil spring 9. This causes the both contact 3a and 4a to come in contact each other again, resulting in the second electrical current flow produced so as to carry out hammering or striking operation against the bell gong to generate the required bell sound. Then the above described operations are repeated.
It is recognized as a drawback with the above described conventional bell sound generating system that it is difficult to select and determine the number of hammering or striking operations per unit time as required, because said number of hammering or striking operations against the bell gong 10 with the use of the hammer 8 is dependent on a variety of factors such as rigidity of the leaf spring 4, weight of the hammer, spring constant of the coil spring 9 and others. Further it is pointed out as another drawback that it is difficult to select and determine the working stroke of the hammer 8 as required, because the movable contact 3a is released from the stationary contact 4a within the very short period of time. Therefore, as far as the conventional bell sound generating system is concerned, it may be concluded that because of the above mentioned drawbacks therewith it is difficult to construct a bell sound generating system on a commercial basis, which has the optimum number of hammering or striking operations and as well as the optimum working stroke of hammer means, in spite of the fact that the number of hammering operations and working strokes at which the maximum bell sounding is produced are available only on the experimental basis.